1. Field of the Invention
The present invention relates to a filtering apparatus, a digital broadcast receiving apparatus and a filtering method applied to, for example, a digital television, a hard disk picture recording device and the like.
2. Related Art
In processing for decoding a transport stream (TS) packet specified by MPEG 2, which is used mainly in digital broadcasting, processing called filtering (PID filtering and section filtering) is required. This will be described in detail below.
The above-mentioned TS packet has a packet structure of 188 bites. The TS packet includes data of voice, video and the like having a PES (packetized elementary stream) format, and SI (service information) or PSI (program specific information) having a section format, as its payload information. An identifier (PID) is allocated to a header of each TS packet, whereby a receiving part (decoding part) can identify what type of data is transmitted by the TS packet.
The above-mentioned SI or PSI (hereinafter referred to as section) is transmitted to the receiving part on a regular schedule for making it possible to acquire media information even if the TS packet is received midway through a program, for example.
The section does not always include same information, and if a change is made to information contents, for example, a history number (version) in a section header, or the like, is changed (e.g. changed from “1” to “2”), whereby the receiving part can determine existence or nonexistence of a change in information.
A TS packet including a plurality of sections may be transmitted by the same PID and in this case, the receiving part can identify each section based on, for example, a table number of the section header or the like. This transmission method is called multi-section transmission and the like.
As can be understood from the above description, in the decoding processing, at least the following filtering is required:
1. filtering for selecting a TS packet by the PID; and
2. filtering for selecting a section if the TS packet selected by the filtering “1” includes the section.
The former is called PID filtering and the latter is called section filtering.
Which PID, with which a TS packet including a section is transmitted, is previously specified by the MPEG standard or broadcasting standard (ARIB in Japan). Namely, which packet selected by PID filtering, for which section filtering is required, is know by the receiving part in advance.